The long term goal of the proposed project is to produce unique high frame rate two-dimensional (2D) and ultimately three-dimensional (3D) images of human heart and cardiovascular systems to improve diagnostic potentials. The current research is designed to 1) study a newly discovered image construction method for both high frame rate 2D and 3D imaging using computer simulations, 2) construct a prototype imaging system capable of high frame rate 2D B-mode imaging (approximately 3750 frames/s for a depth of 200 mm), and 3) evaluate the method in vitro and in vivo using the prototype system. The current goal will be achieved through the following specific aims: Specific Aim 1: Study of Fourier Construction Method. We will study the theory of the new Fourier image construction method for ultra high frame rate 2D and 3D imaging. Influence of nonuniform frequency-dependent attenuation and phase aberration on the images will be studied with computer simulations. Implementation of the method with simplified hardware will be investigated. Study of limited diffraction beams will continue. Specific Aim 2: Development of a Prototype 2D Imaging System. A prototype 2D high frame rate imaging system will be constructed. This includes the development of a multichannel array transducer, transmitter, and receiver. The system will also have the capabilities of beam steering, on-line image construction, and electrocardiogram (ECG) controlled data acquisition. Specific Aim 3:In vitro Evaluation of the New Imaging Method. The Fourier construction method will be evaluated with the prototype system in vitro, on tissue-equivalent phantoms, tissue samples, and flow phantoms. Specific Aim 4: Preliminary In Vivo Studies. The Fourier construction-method will also be studied in vivo with the prototype system. A limited number of volunteers and patients will be studied. Both high frame rate 2D tissue and flow images will be constructed and evaluated by physicians for their diagnostic potentials.